This is not true. The town of Radisson was built in the 70s during work on the James Bay Project and is still mainly francophone. It's about 2° north of Dunkirk.

https://en.wikipedia.org/wiki/Radisson,_Quebec

Interesting but I'm not sure I'm buying it ;-) Radisson is a small unconstituted locality so whether it qualifies as a town is questionable. It also has a population small enough to fit in two or three buses.

How about Fermont in Quebec, then? http://www.toponymie.gouv.qc.ca/ct/ToposWeb/fiche.aspx?no_se...

It is predominantly French speaking, is 1° further north than Dunkirk, is incorporated as Ville de Fermont, has a population of about 2400.

It also has a Wikipedia page that claims "Fermont is arguably the world's northernmost Francophone settlement of any considerable size": https://en.wikipedia.org/wiki/Fermont.

It's much cooler that Dunkirk should hold this distinction, isn't it, so can we agree please that these rather undistinguished places in Canada don't count? Anyway Dunkirk is a proper town/city (91K people, interesting history) not like this awful sounding place where everyone lives in a single building because it's like the moon there or something.

I did wonder about Belgium but it looks like most of Belgium (and all of the French speaking parts) are further south than Dunkirk.